Without doubt the most exciting episode of the modern series to date, if not the best ever, ended last night with the prematurely aged Doctor staring out at the ongoing destruction of one-tenth of the human race and left us breathlessly waiting for the concluding part next week but at the same time wishing this series would never end. With six billion Toclafane descending on the planet, his TARDIS a wreck, and struggling for breath through lungs a hundred years older than they were only minutes before, how on Earth is the Doctor going to get out of this one?

The Doctor, Martha and Captain Jack pop back into 21st century London courtesy of Jack’s Vortex Manipulator, which has been given a new lease of life thanks to the Doctor. Martha immediately recognises the posters of Harry Saxon – before she met the Doctor she was intending to vote for him. Saxon has been busy building up his campaign for the premiership for eighteen months. Even though the Doctor managed to freeze the TARDIS’ co-ordinates, Saxon, aka The Master, still had enough leeway to make his plan a reality.

Having been duly elected, Saxon despatches the toadying cabinet with a quick blast of noxious gas and turns his attention to more pressing matters: the introduction of his new friends the Toclafane to London society. His wife has been sidetracked by an “interview” with Vivian Rook which turns out to be an attempt to warn her that her husband is not what he seems. In fact despite having a long and well-documented “history” he didn’t exist at all until 18 months ago. Lucy Saxon isn’t impressed – she’s already in on the deal – and husband Harry has been listening from the next room to Vivian’s attempt to discredit him. The spinning, hovering Toclafane deploy some sharp armoury and make short work of Ms. Rook.

Saxon broadcasts to the nation, and the world, that after recent strange goings-on and otherwordly contact (the Slitheen ship, the Cybermen, …) he has been contacted directly by another race who are keen for Earth to join with the rest of the galactic community. First Contact will be achieved at 8am the next day. The news is greeted with some annoyance in the United States, where the president doesn’t take kindly to being supplanted in the extraterrestrial contact stakes.

Meanwhile back at Martha’s place, the broadcast is rudely interrupted by the presence of a bomb connected to the telly. A bomb which the Doctor only discovers in the nick of time. The entire first floor explodes as they are running across the street. Martha calls her mother. She’s not convinced by her mother’s story that she’s getting back together with Martha’s Dad. It’s a trap and when Francine passes him the phone to back up her story, Martha’s Dad bravely seizes his chance to tell her to RUN!

Saxon has been listening in on this conversation, but Martha is only bait. Once he realises who she is speaking with, the Doctor grabs the phone. He learns that the Master was resurrected by the Time Lords to fight with them against the Daleks. They needed a warrior and he was the best they could think of, but he repayed them by running away and making himself human so they couldn’t find him. Not that there was anyone left to go looking after a while. The Doctor offers to work with the Master, but we all know that’s never going to work out. With the Master controlling the thoughts of the populace, our heroes are being treated as terrorists and the whole country is on the lookout for them.

And how is he controlling them exactly? Luckily for our three intrepid buckaneers Vivian Moss has emailed her report to Torchwood, revealing exactly what the Archangel network is. A pan-global communications network that carries all mobile phone traffic, no matter who your airtime provider is. And hidden within that network, and delivered to every mobile phone as part of every call: the sound of drums. The maddening beat that the Master hears every waking moment, and which he can use to control everyone’s thoughts.

The Doctor creates a way for his team to “hide” – a perception filter made from bastardised parts of Jack’s laptop and a TARDIS key. When wearing them, provided none of them brings attention to themselves, no-one will notice them.

In preparation for the 8am meeting with the Toclafane, the President of the United States has flown to Britain in Air Force One and announces to Saxon that he is taking over and the operation is now in the hands of UNIT. The rendezvous with the extraterrestrials will take place on the carrier Valiant.

The Doctor, Martha and Jack teleport to the Valiant using the Vortex Manipulator. Martha is surprised to find the ship is not sailing in the sea – it’s sailing in the sky! Like a refugee from Captain Scarlet it hangs above the Earth, protecting everyone. For the time being. Our heroes discover the TARDIS, but their joy soon turns to desperation as they find the Master has ripped out the guts of the beloved device and turned it into a paradox machine. The Doctor is horrified, and you get the distinct impression we will be too, once we find out exactly what a paradox machine is.

President Arthur Coleman Winters, his ego inflated beyond all reason, stands to welcome the visitors on behalf of “the citizens of the United States and the people of Earth.” Trouble is, the Toclafane don’t like him much. They want the Master. And the Master’s first request of them is to kill Winters, which they do with terrifying speed. The game is up as Saxon finally reveals himself to all as the Master, brandishes his laser screwdriver (“who needs sonic?” Excellent!) and kills Jack. For the time being.

But the Master’s screwdriver is not only a destructive force. He’s also built in Lazarus‘ technology and uses it to devastating effect on the Doctor – aging him a hundred years in a few seconds. Jack, who’s recovered rapidly from being dead, hands Martha his Vortex manipulator and tells her she has to get out so she can save them. Meanwhile, the Master announces the end of the world and signals the arrival of the Toclafane. The sky splits and billions of the spinning spheres descend, their weapons glittering in the morning sun. Six billion of them to be precise – one for every human on the planet.

“Decimate them,” shouts a maniacal Master, “kill one-tenth of all human life.” Thus RTD proves that not only does he love Doctor Who, he also loves English. An entire generation of new Who fans now know the correct definition of “decimate.” Wonderful stuff.

Martha transports to the planet’s surface and vows, Terminator-style, to be back. And back aboard the Valiant, a horrified and wheezy Doctor gazes down on the wanton destruction of his favourite planet and its brave but seemingly doomed inhabitants.

Superb! A nail-biter from start to finish and full of delicious wit and nods not only to past episodes of this series, which we’ve come to expect from the series finale, but also to Who folklore and memories of the Pertwee era and the many adventures he had with UNIT. Excellent crossover with Torchwood too, the Doctor’s disgust at discovering Jack’s involvement instantly tempered by Jack’s insistence that he built it back up differently, better, and he did it in honour of the Doctor. Truly, this story had it all, and things are shaping up for this to be the blockbuster series end of all time. You do not want to miss next week’s final instalment. I think I might even set TWO videos, just to be sure.

Next week: The Last of the Time Lords (and the last of this series! *sniff*)